APA Monitor, April 1989
The APA Monitor was (and, according to Google, still is) the official publication of the American Psychological Association. Cartoons appeared only sporadically in its pages when this was printed in 1989, and I'm pretty sure that they have disappeared completely by now.
This gag is another one of my personal favorites, by the way. In my opinion it belonged in The New Yorker, but of course I was glad to see it in the APA Monitor, after it was rejected by all of my top markets.